Scanning probes are non-contact optical probes for measuring thousands of points a second on the 3D surface shape of an object. There are three broad types of scanning probe: point, stripe and area. Most stripe scanning probes use the principal of optical triangulation.
In order to scan the surface of an object, a stripe scanning probe needs to move over the object's surface in a similar way to how a paintbrush is used for painting a surface. The movement of the stripe scanning probe may be accomplished manually or by automated equipment.
In order to obtain accurate data of the surface of an object, a localiser may be used to register the position and orientation of the stripe scanning probe when surface data is captured by the stripe scanning probe. Localisers are generally mechanical or remote. Localisers may also have the dual functionality of supporting/moving the probe as well as supplying its position and orientation. Mechanical localisers include: 3-axis Cartesian coordinate measurement machines (CMMs), Manual CMM arms, Robot CMM arms and essentially all types of combinations of continuous mechanical linkages that might accurately register the position and orientation of a probe end relative to a base end, the stripe scanning probe being rigidly attached to the probe end. Remote localisers include: optical trackers, optical CMMs, magnetic trackers and GPS systems. Remote localisers often require one or more lines of sight between the stripe scanning probe and the remote localiser equipment.
Manual CMM Arms have the flexibility of being able to access areas with difficult access. Manual CMM Arms are acceptably accurate for many applications, but are not automated; they are expensive to operate, particularly since a semi-skilled operator is required; human operators are also subject to human error. As examples, U.S. Pat. No. 3,994,798, U.S. Pat. No. 5,402,582, U.S. Pat. No. 5,829,148 and U.S. Pat. No. 6,366,831 disclose background information on Manual CMM Arms. Stripe scanning probes on Manual CMM Arms were disclosed by Crampton, in U.S. Pat. No. 6,611,617.
Stripe scanning probes are generally mounted offset on the side of the Manual CMM Arm or mounted on the probe end of it. Stripe scanning probes are usually quickly dismountable from a Manual CMM Arm using a mounting system that is mechanically repeatable to an acceptable degree of accuracy.
Robot CMM Arms and their use with stripe scanning probes were disclosed by Crampton, in U.S. Pat. No. 7,395,606 and U.S. Pat. No. 7,591,078. Robot CMM Arms have the advantage over Manual CMM Arms of supporting and moving the stripe scanning probe automatically. Both Manual CMM Arms and Robot CMM Arms have the advantage over Cartesian CMMs of articulation.
U.S. Pat. No. 6,141,105 discloses a three-dimensional measuring device, which uses a zoom unit with an autofocus function. US Patent Application 2009/0080036 discloses a scanner system, which uses a lens system for focusing an image onto the sensor element. US Patent Application 2007/0097381 discloses a three-dimensional metrology imaging system, which uses interchangeable lenses.
In the market, the user requirement of a scanning probe includes one or more of the following: Accuracy: Users demand ever higher accuracy and data quality from their stripe scanning probes; Mechanical stability: Users demand mechanically stable strip scanning probes; Long-term reliability: The optical systems within the scanning probe should not have to be recalibrated regularly; Speed: When surfaces are scanned, they are sampled. The quality and automation of the surface reconstruction or measurement is related to the number and density of raw points scanned. Scanning rates of current sensors on the market are typically 3 000 to 20 000 points per second. Rates exceeding 200 000 points per second will increase the productivity of the stripe scanning probes by reducing both data capture time and manual intervention in the post-processing activity; Compactness: It is desirable to provide a stripe scanning probe with built in processing and without an extra box of electronics and associated cables; Weight: It is desirable to provide a stripe scanning probe that weighs less; Cost: The market place is becoming more competitive and reductions the manufacturing cost of stripe scanning probes are therefore desirable.